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Light学术出版中心
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Issue 11 ， 2023
- Abstract：To realize the high-precision position measurement of freeform surfaces， this paper proposes an optic-mechanical reference positioning method that employs a position measurement model. First， an optical-mechanical reference positioning method based on a coordinate measuring machine and computer-generated holography is proposed. Then， using a spherical mounted retroreflector （SMR） target ball， cat eye， and reference ball as the benchmarks， three benchmark position measurement models are established on the basis of wave aberration theory and parallax effect. The functional relationship between the position error and the wavefront aberration in the reference area is obtained， and the three position measurement models are compared and analyzed. Finally， the three benchmark position measurement methods are simulated and validated via experiments. The residual difference between the measurement results and the model is below 0.05λ， and the relative error is below 2.43%， confirming the accuracy of the model. The experimental results indicate that the axial positioning error of the cat-eye method is 24 μm when the measurement distance is 1 000 mm. The axial positioning error of the reference-ball method is 50 μm. The SMR target ball positioning error is 16 μm in the axial direction， 1 μm in the X and Y directions， and 3.26″ in clocking. The SMR target ball method has the minimum positioning error， maximum measurement dynamic range， and maximum degree of freedom in detecting optical elements； therefore， it is more suitable for high-precision pose measurement of freeform surfaces.Keywords：optical testing;optical surface posture measurement;computer generated holography;optic-mechanical reference positioning method;positioning error
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Published：2023-07-08 - Abstract：High-precision displacement measurement can help realize high-precision microgravity， which can further sever a variety of space science payloads for research missions. In this study， we devised a dual-frequency interferometer based on three sets of orthogonal symmetric cube corner retroreflectors （CCRs） for measuring the six-degree-of-freedom （6DOF） pose of the spatial inertial test mass （TM） through heterodyne detection. We first established an optical model of the actual CCR， which considers the optical path difference caused by the motion of the TM， and derived the analytical relationship between the pose of the TM and the measured optical path change. Then， the attitude angles and displacements of the TM were calculated using the method of numerical analysis， which affords remarkably higher accuracy than does the traditional small-angle approximation method. Furthermore， the performance of our system was estimated using space in-orbit data and random data. The simulation results show that the displacement error was less than 0.02 fm even when the TM vibrated significantly， indicating that our method affords high accuracy and good adaptability. In addition， the error sources of the system were analyzed. The measurement errors for the attitude angle and displacement are less than 0.017° and 10 nm， respectively， when the angular installation error is below 5 mrad， the distance installation error is less than 10 μm， and the parallelism is less than 2 mrad. The proposed 6DOF measurement and calculation method can also be used in various precision machining and detection applications.Keywords：precision measurement;heterodyne interference measurement;dual frequency laser interference;microgravity;inertial sensing;six-degree-of-freedom
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Published：2023-07-08 - Abstract：The laser beam stabilization system facilitates high-precision correction of the laser beam via the control of the beam position and angle， providing long-term stability. It plays an important role in micro/nano-laser direct writing and super-resolution imaging. In this paper， a miniaturized laser stabilization system with error separation technology， which eliminates the coupling error caused by traditional dual-mirror controlling and improves the performance of laser beam stabilization control， is proposed. Comparative experiments indicate that the laser stabilization system based on this method stabilized the beam position with an accuracy better than 0.3 µm （RMS） and stabilized the angle with an accuracy better than 1 µrad （RMS）. The results of test experiments with active disturbance indicate that the system maintained the same performance. Compared with two commercial laser stabilization systems under the same conditions， the proposed system can yield 50% lower position and angle jitter.Keywords：laser stabilization;high-precision correction;high precision angle detection;error separation technology
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Published：2023-07-08 - Abstract：In the current spectral simulation method based on a digital micromirror device （DMD）， the spectral simulation units have different bias properties and nonlinear modulation； thus， a spectral simulation method for multi-color temperature modulation is lacking. This paper presents a fuzzy proportional-integral-derivative （PID） control-based stellar spectral simulation method. First， the DMD working matrix， spectral modulation weight matrix， spectral distribution function matrix， and target spectrum matrix are constructed. Next， a spectral distribution function fitting algorithm based on a genetic algorithm-optimized backpropagation （BP） neural network is studied. The BP neural network algorithm and the basic elements of the genetic algorithm are designed and used to achieve spectral distribution function fitting in the peak wavelength region of 400-800 nm. Then， a spectral simulation algorithm based on fuzzy PID control is proposed. The fuzzy set and affiliation function are selected， and the fuzzy inference and defuzzification rules are formulated. The fuzzy PID controller is simulated and analyzed， and the results indicate that the overshoot of fuzzy PID control is reduced by 90.7% and the regulation time is shortened by 69.4% compared with those of PID control. Finally， the simulation accuracy of the color temperature spectral distribution curve in the range of 3 000-11 000 K is verified via experiments. According to the results， the spectral simulation error is better than ±4.21%. Compared with the PID control， the maximum spectral simulation accuracy of fuzzy PID control at 3 000， 6 500， and 11 000 K is increased by factors of 2.31， 1.71， and 2.02， respectively. The proposed method can increase the spectral simulation accuracy， providing the theory and foundation for the development of high-precision star-sensitive devices.Keywords：spectral simulation;Fuzzy control;genetic algorithm;digital micromirror;BP neural network algorithm
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Published：2023-07-08 - Abstract：The Gaofen-14 （GF-14） satellite is equipped with a three-beam laser altimeter system aimed at assisting the two linear-array optical camera to perform global 1∶10 000 mapping without ground control points. Owing to mechanical vibration and environmental changes， the geometric parameters of the laser altimeter would deviate from those measured in the laboratory； thus， it is necessary to perform high-precision on-orbit geometric calibration. In this study， a strict geometric model of the laser footprint was constructed according to the characteristics of the GF-14 laser load. Through atmospheric correction and tidal correction， the laser spot captured by the ground detector array was used to perform on-orbit geometric calibration and accuracy verification. The test results indicate that the elevation accuracies of the GF-14 three-beam laser altimeter are 0.190， 0.256， and 0.220 m， which satisfy the design target and can be used as the elevation control point for operational production.Keywords：GF-14 Satellite;laser altimeter;on-orbit geometric calibration;accuracy verification;elevation control point
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Published：2023-07-08
Modern Applied Optics
- Abstract：Aiming to compensate for the cross-periodic coupling of piezoelectric nano-stages with measurement delays in raster nano-scanning， particularly in high-speed scanning applications， this paper presents a robust periodic disturbance observer （PDOB） control strategy that does not require solving complex inverse models. First， an electromechanical multi-perturbation model is developed to describe the dynamic behavior of piezoelectric stage systems. Then， a PDOB control structure based on the model is constructed. The problem of optimal controller parameter solution is transformed into a mixed sensitivity optimization problem for time-delay systems with the formulated performance optimization function and robust stability condition， which is solved via the infinite-dimensional H∞ control method. Finally， comprehensive experimental investigations are conducted on the piezoelectric nano-stage. The results indicate that the developed dynamic model can effectively fit the experimental response of the stage and that the proposed robust periodic disturbance control method has superior anti-disturbance and uncertainty compensation performance to the method without disturbance observer and the conventional PDOB control method， with improvements of >99% and >50%， respectively， in the anti-disturbance performance at the fundamental harmonic frequency.Keywords：piezoelectric nano-stage;coupling compensation;dynamic modeling;periodic disturbance observer;time delay;H∞ optimization
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Published：2023-07-08 - Abstract：To develop a low-stress laser welding process for the corrugated diaphragm of a pressure sensor， a process scheme for the welding of the corrugated diaphragm using laser welding technology is designed， an optimization method for the key welding process parameters based on an orthogonal test is proposed， the orthogonal test table of the welding process is designed， and an orthogonal test with the residual stress of welding as the evaluation index is completed. Based on the best combination of welding process parameters obtained via the orthogonal test， the pressure sensors are welded， and the testing and verification of welding sealing， tensile strength， and static performance indicators of the sensors are completed. The experimental results indicate that a laser power of 350 W， pulse frequency of 150 Hz， pulse width of 1.5 ms， and turntable speed of 4 200 （°）/min are the optimal combination parameters of the laser welding process for the corrugated diaphragm of the pressure sensor； a rough calculation value of 499.60 MPa is obtained for the weld tensile strength of the pressure sensor， and the weld has a good sealing property. After welding the corrugated diaphragm， the zero output of the sensor is increased by approximately 17%， and indices such as sensitivity， full-scale output， nonlinearity， hysteresis， and repeatability exhibit little change. However， the nonlinearity， hysteresis， and repeatability are approximately two times better than those of the same type of sensor from the same manufacturer. The optimal laser welding process determined via the orthogonal test can ensure the high-quality packaging application of pressure sensors.Keywords：pressure sensor;Corrugated diaphragm;laser welding;residual stress;orthogonal test;Static performance
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Published：2023-07-08 - Abstract：To reduce the electromagnetic radiation emission intensity of airborne digital equipment， the spectrum of the digital signal is analyzed， revealing that the fundamental wave and its high-frequency harmonics are the sources of electromagnetic radiation emissions. Next， the rationale of shielding layer to suppress electromagnetic radiation is analyzed. The results indicate that the high-conductivity non-magnetic shielding layer has a good shielding effect on the electric field and high-frequency magnetic field. The influence of the gap on the shielding effectiveness of the shield is analyzed again， and a new method of double-layer fill shielding is proposed and validated. Then， the absorption loss of the electromagnetic wave is analyzed， and a new method for improving the shielding effectiveness of twisted-pair shielded cable/coaxial cable double-layer shielding is proposed and validated. Finally， an actual engineering project is considered as an example. The project equipment satisfies the GJB151B-2013 RE102 requirements and still interferes with the Beidou equipment Star（BDS） Searching and positioning. The electromagnetic compatibility is improved using the proposed method. After the improvement， the emission intensity of electromagnetic radiation is significantly reduced， by 12 dBμV/m on average. The ground and flight experiments verify that the integral power of the BDB1 and BDB3 frequency points is increased by 0.59 and 1.84 dBm， respectively， under normal operating conditions， and the number of BDS searching satellites is increased from ≤3 to ≥9， the BDS can operate normally.Keywords：digital equipment;Electromagnetic compatibility;double-layer shielding;double-layer fill shielding;shielding effectiveness
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Published：2023-07-08
Micro/Nano Technology and Fine Mechanics
- Abstract：Non-metallic forest balls are often used to evaluate the measurement uncertainty of industrial computed tomography （CT） detection involved the material and scale of parts actually are large， which has introduced the problem of insufficient applicability and reliability. In this study， the uncertainty of industrial CT measurement was evaluated according to forest balls made of different materials， and the effects of the materials on the uncertainty were examined. First， we designed and fabricated three types of standard forest balls with different materials and calibrated them using a CMM according to the commonly used measurement range of industrial CT. Then， we performed evaluation and analysis of the measurement uncertainty for the diameter and center distance from forest balls based on industrial CT scanning and measuring. The results indicated that the influence of the material on the expanded uncertainty of diameter measurement from the forest balls was insignificant. The expanded uncertainty of measurement from the balls increased with the ball center distance， and the expanded uncertainty of non-metallic balls， including a ceramic ball and ruby ball， was essentially the same： approximately 0.003 5 mm. In comparison， that of a steel ball was 3.4 times larger， reaching 0.012 2 mm. There exists a certain system error in ball center distance measurement， however， the material influence on the standard forest balls is not evident. Center distance measurement based on forest balls of different materials has engineering value for evaluating the selection and calibration of industrial CT measurement uncertainty.Keywords：Industrial Computed Tomography;measurement uncertainty;forest balls;geometric dimensions
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Published：2023-07-08 - Abstract：Using deep learning methods to retrieve mineral abundance requires numerous labeled hyperspectral data samples. Thus， a method based on the Hapke mixed model with filling factor is proposed for data augmentation of small mineral samples， to generate a large number of labeled datasets. First， five kinds of common mineral powders were mixed by multiple elements in the laboratory according to the weight mixing ratio， and the spectra of mixed minerals were measured. Subsequently， mixing spectra were simulated considering the corresponding weight proportion of the five mixing models， including the linear mixing model. The simulated spectra of the augmented data using the original Hapke and the Hapke mixing model with filling factors of 0.1， 0.2， and 0.3 were compared with the measured spectra. Finally， based on the sum to one abundance matrix randomly generated by the Monte Carlo method， forty thousand simulated spectra were generated using the five mixing models. The abundance information on real spectral data was obtained by treating the simulated spectra as the training dataset of the stack autoencoder network. The results showed that the simulation results obtained using the original Hapke model and the model with filling factors were better in accuracy than those of the linear mixed model. When the filling factors of the Hapke model were set to 0.1 and 0.2， the mean SAM error was 0.053 5 and 0.053 7， respectively， and the RMSE error of mineral abundance inversion of hyperspectral data was 0.124 8， demonstrating the superiority of the Hapke model with filling factors over the other four methods. The simulated mineral spectrum was closer to the measured spectrum and better than that without any filling factors with a simulation error of 0.074 8， and the spectra associated with the simulated data were closer to the real spectrum， thereby providing support for mineral abundance inversion research based on deep learning.Keywords：hyperspectral technique;deep learning;simulating spectra;mixing model;Hapke model;data augmentation;abundances inversion
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Published：2023-07-08 - Abstract：To address the inaccurate measurement of cylindrical surface defects caused by perspective projection in machine vision systems， an image correction method to resolve cylindrical surface perspective projection distortion is proposed. In this method， the image area of the cylinder is first extracted. Then， the transverse and axial directions are determined. On the basis of the perspective projection characteristics of the cylindrical surface， the distortion is divided into axial and transverse deformation. The imaging parameters and cylindrical radius are utilized to establish the corresponding relationship between the coordinates of the original image and the those of the corrected image. The perspective projection distortion is corrected by pixel mapping and nearest neighbor interpolation. The experimental results demonstrate that the proposed method affords a good correction effect on images of different-diameter cylindrical surfaces. Both near-large and far-small perspective deformation and oblique projection deformation are eliminated in the corrected images. For the checkerboard simulation correction， the measurement error for the side length of the six cylindrical checkerboard squares decreases from a highest of 14.9% before correction to 1.2% after correction. In a scratch measurement， the maximum errors in the original image of two cylinders of different diameters are 78.0% and 61.8%. After correction using the proposed method， the maximum errors are only 5.9% and 5.5%， respectively. The remarkable correction effect verifies the effectiveness of the method.Keywords：image correction;cylindrical surface;perspective projection;distortion;measurement
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Published：2023-07-08 - Abstract：The efficient extraction of buildings from remote sensing images plays an important role in urban planning， disaster rescue， and military reconnaissance. Building extraction methods based on deep learning have made significant progress in accuracy， especially with the sparse token transformer network （STTNet） achieving extremely high accuracy. However， these methods are usually implemented using complex convolution operations in extremely large network models， which results in low extraction speed， thereby presenting difficulties in fulfilling practical needs. Therefore， in this study， a method is designed for the fast extraction of buildings from remote sensing images. First， multi-scale convolution is introduced into the feature extraction network of the STTNet model， whereby multi-scale features are extracted in the same convolution layer to further improve the feature extraction capability of the model. Second， channel attention is applied to the feature map of the force weights， to effectively learn channel attention weights， thereby solving the problem of floating channel attention weights when using the backbone network to output the learned feature map. Finally， to reduce the number of model parameters and speed up the model， the STTNet model structure is changed from parallel to series. Experiments on the INRIA building dataset show that in terms of accuracy and the intersection over union （IoU） metric， the proposed method is 18.3% faster than STTNet and thus better than current mainstream methods.Keywords：remote sensing image;building extraction;multi-scale convolution;sparse feature extractor
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Published：2023-07-08 - Abstract：The slave controller is a fundamental component for realizing bus communication， field sensor acquisition， motor， and other actuator control functions in the industrial automation control system. To meet the needs of various industrial field actuators and sensors and to solve the problems of the cumbersome hardware and software design， low development efficiency， and difficult upgrading and transplantation of slave controllers， this paper proposes a model development method for slave controllers that involves analyzing the hardware and software components of typical slave controllers. The common real-time Ethernet communication processing model of slave controllers and the device control models of digital input/output （I/O）， analog I/O， motion control， and communication interface conversion slaves in practical applications are established， and the model code is automatically generated and ported to realize the standardized and rapid development of slave controller software on the domestic hardware platform. The experimental results verify the effectiveness of the proposed model development method. This study provides a new method for the rapid development and upgrading of the localized slave controller software.Keywords：industrial automation;control system;real-time ethernet fieldbus;model based design
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Published：2023-07-08
Information Sciences
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